Oelschläger H H A, Ridgway S H, Knauth M
Institute of Anatomy III, Johann Wolfgang Goethe University, Frankfurt a.M., Germany.
Brain Behav Evol. 2010;75(1):33-62. doi: 10.1159/000293601. Epub 2010 Mar 5.
This study compares a whole brain of the dwarf sperm whale (Kogia sima) with that of a common dolphin (Delphinus delphis) using high-resolution magnetic resonance imaging (MRI). The Kogia brain was scanned with a Siemens Trio Magnetic Resonance scanner in the three main planes. As in the common dolphin and other marine odontocetes, the brain of the dwarf sperm whale is large, with the telencephalic hemispheres remarkably dominating the brain stem. The neocortex is voluminous and the cortical grey matter thin but expansive and densely convoluted. The corpus callosum is thin and the anterior commissure hard to detect whereas the posterior commissure is well-developed. There is consistency as to the lack of telencephalic structures (olfactory bulb and peduncle, olfactory ventricular recess) and neither an occipital lobe of the telencephalic hemisphere nor the posterior horn of the lateral ventricle are present. A pineal organ could not be detected in Kogia. Both species show a tiny hippocampus and thin fornix and the mammillary body is very small whereas other structures of the limbic system are well-developed. The brain stem is thick and underlies a large cerebellum, both of which, however, are smaller in Kogia. The vestibular system is markedly reduced with the exception of the lateral (Deiters') nucleus. The visual system, although well-developed in both species, is exceeded by the impressive absolute and relative size of the auditory system. The brainstem and cerebellum comprise a series of structures (elliptic nucleus, medial accessory inferior olive, paraflocculus and posterior interpositus nucleus) showing characteristic odontocete dimensions and size correlations. All these structures seem to serve the auditory system with respect to echolocation, communication, and navigation.
本研究使用高分辨率磁共振成像（MRI），将侏虎鲸（Kogia sima）的全脑与普通海豚（Delphinus delphis）的全脑进行了比较。使用西门子Trio磁共振扫描仪在三个主要平面上对侏虎鲸的大脑进行了扫描。与普通海豚和其他海洋齿鲸一样，侏虎鲸的大脑很大，端脑半球明显占据脑干的主导地位。新皮质体积大，皮质灰质薄但扩展且密集卷曲。胼胝体薄，前连合难以检测到，而后连合发育良好。在端脑结构（嗅球和嗅束、嗅脑室隐窝）的缺失方面存在一致性，端脑半球既没有枕叶，侧脑室也没有后角。在侏虎鲸中未检测到松果体。两个物种都显示出海马体小、穹窿薄，乳头体非常小，而边缘系统的其他结构发育良好。脑干粗壮，其下方是一个大的小脑，然而，在侏虎鲸中两者都较小。除了外侧（代特氏）核外，前庭系统明显缩小。视觉系统虽然在两个物种中都发育良好，但在绝对和相对大小上都比不上令人印象深刻的听觉系统。脑干和小脑包含一系列结构（椭圆核、内侧副下橄榄核、旁绒球和后间位核），显示出典型的齿鲸尺寸和大小相关性。所有这些结构似乎都为听觉系统在回声定位、通信和导航方面提供服务。
